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MilliSecs - Where does it end?Explains the limitations of MilliSecs() and how to use it effectively. |
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Introduction Some believe that MilliSecs () returns the number of milliseconds elapsed since midnight. Unfortunately, this is not the case. The MilliSecs () function returns the number of milliseconds elapsed since Windows was first started. So right after windows starts, MilliSecs () equals zero. Over the edge Since the maximum value of an integer in Blitz is 2,147,483,647 MilliSecs () will be counting up to that value. How long will that take? Although most people don't have their computer on that long. Besides, it's pretty hard to keep Windows stable for such a long time anyway  So what happens after that time? Take a regular integer variable for example. And you assign the maximum value to it. Now add 1 and see what happens. It wraps to -2,147,483,648! Same thing happens with the milliseconds. Problem What is the problem about all this? Imagine you have the following code: If the number of milliseconds wrap in the middle of the Repeat..Until, the program could hang forever! If Finish lies right before the wrapping point and our program didn't have enough time to check MilliSecs before it wraps, the resulting value will be even smaller than before, and remaining smaller than Finish for another 50 days! Solution So what's the solution you ask? The solution is simply changing orientation to difference. Say what you say? I mean, by comparing difference instead of points in time you can still accurately measure time without running into any gaps in time. If you look at the graph above and then at the following equation: Then you might wonder why it works. Reality check Let's try it out in a program. Which should give you 96. Here's what happens: And that's all there is to it 
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